Potential 4th class

Many modern class-based shooters start off at launch with a 4 class system, whether it's Battlefield, Borderlands, or Evolve. These classes usually consist of: a Marksman/Gunslinger (Hunter), Heavy/Gunner (Titan), Healer/Wizard (Warlock), and finally the Tactical/Engineer.
However Destiny has no class that fills the tactical class ideology, so I propose that a 4th class could be implemented into the game without causing too much of an overlap between classes.
What do you think a Cool/Balanced 4th class would be? And what role would this class play?
This would obviously not be in Destiny 1, but in the sequels.
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